Remote plasma deposition systems, such as plasma-enhanced chemical vapor deposition (PECVD) systems and plasma-enhanced atomic layer deposition (PEALD) systems, as well as remote plasma etching and treatment systems can be used for a variety of purposes. For example, remote plasma deposition systems can be used to deposit thin films of material onto a substrate, and the remote plasma etching and treatment reactors can be used to etch material from a substrate, clean a reactor surface, treat a substrate surface, and/or treat a reactor surface.
In general, remote plasma systems include a reactor having a reaction chamber, one or more gas sources coupled to the reaction chamber, and a remote plasma source between one or more gas sources and the reaction chamber. Remote plasma systems are thought to be advantageous over thermal systems for some applications, because the remote plasma can generate excited reactive species at relatively low temperatures, allowing reactions to take place at effectively lower temperatures. Remote plasma systems may also be advantageous over direct plasma systems, because, unlike direct plasma systems, remote plasma systems do not form a plasma directly over a surface of a substrate or within a reaction chamber. As a result, surface damage to a substrate or reaction chamber that might otherwise occur in a direct plasma reactor can be reduced or eliminated.
Excited or energized species from a remote plasma reactor may desirably be pulsed to a reaction chamber. For example, a PEALD process typically includes pulsing a first reactant to a reaction chamber followed by a pulse of a second reactant, where the first reactant, the second reactant, or both may include species formed from a remote plasma.
One technique for providing a pulse of excited species from a remote plasma source to a reaction chamber includes pulsing the power to the remote plasma source. However, remote plasma units may require a lengthy pre-ignition step (e.g., in argon or nitrogen) for each power cycle. Thus, throughput on such systems may be relatively low.
Other techniques for providing a pulse of excited species from a remote plasma unit to a reaction chamber include switching a flow of excited species exiting the remote plasma unit from the reactor input to a vacuum source or bypass for each pulse. However, remote plasma sources are typically designed to operate at steady-state conditions, where a flow rate of gasses to the plasma source and an operating pressure of the plasma source are held relatively constant. Even slight variations in flow rates or pressure may cause significant changes in the plasma and therefore the reactive species exiting the remote plasma unit—or even extinguish the plasma. Thus, diverting the flow from a reactor to a vacuum source or bypass affects the characteristics of the effluent from the remote plasma unit and may cause the plasma to extinguish.
Accordingly, improved methods and systems for providing a pulse of excited species from a remote plasma source to a reaction chamber are desired.